Optimal Battery Sizing for Large-Scale Solar-PV Generation to Improve Frequency Stability

This paper analyses the impact of large-scale solar-photovoltaic (PV) generation on power system frequency stability and proposes a methodology to size the battery energy storage system (BESS) to mitigate the adverse effects from the solar-PV generation on frequency stability. The proposed methodology for sizing the battery is based on the requirement of recovering the frequency nadir back to the original value (i.e., when the power system is soley operated with synchronous generators). Multi-machine reliability and voltage stability (RVS) test power system model is used for the investigation while considering an outage at the largest generation unit. The results show that when synchronous generators located near to the disturbance are replaced by the solar-PV plant, the impact of the solar-PV on frequency stability is less in comparison to the case where synchronous generators located far away from the disturbance are replaced by the solar-PV plant. Since the impact on frequency stability is comparatively low for the case with solar-PV located near to the disturbance, a smaller sized BESS is required to improve the frequency nadir, whereas a large BESS is required for the solar-PV when it is sited far away from the disturbance. Therefore, proximity of the solar-PV plant to probable fault locations is a key determinant of the size of the BESS.